Star removal

[shropshire lad]

Is there a programe that will remove the stars from my image so I can play with the background.

Or may be even a way to do it in photo shop

Paul

 

[Budgie1]

There's StarNet and StarXTerminator. 

I don't use PS for this, so can help on that side.  

 

[OK Apricot]

I use StarXTerminator in photoshop. Very good plug in, does a great job of removing stars and leaves minimal artifacts if any. Really helps you focus on nebula, dust etc. 

[shropshire lad]

51 minutes ago, OK Apricot said:

I use StarXTerminator in photoshop. Very good plug in, does a great job of removing stars and leaves minimal artifacts if any. Really helps you focus on nebula, dust etc. 

I have downloaded that plug in but it just crashes my photo shop.

 

[OK Apricot]

Ah, computer spec is a bit above my head, but I'll say my Thinkpad T430 is an i5 processor dual core, I think 4gb ram and no graphics processor but still manages StarXTerminator (albeit taking around 10 mins!). I think photoshop has a pop up window upon opening where it shows how compatible your system is? 

[The Lazy Astronomer]

Not sure about StarX, but for Starnet, your CPU must support the SSE2 instruction set - if you're using a fairly old machine it may not have support for it.

[Elp]

What version of PS have you got? The modern ones have a similar function built in, which you can try first. Alternatively starnet is free which you can also try. It's not essential, I still process with stars in the image.

Edited November 14, 2022 by Elp

[shropshire lad]

43 minutes ago, Elp said:

What version of PS have you got? The modern ones have a similar function built in, which you can try first. Alternatively starnet is free which you can also try. It's not essential, I still process with stars in the image.

I have the latest version 2023 , and what is the built in function please ?

 

[Elp]

I haven't used it myself as mines old, but I believe you can (everything up to the last point is an essential skill in manual processing for star control/editing):

1. Select > colour range > highlights

2. Your stars should now all be selected, if there's bright nebulosity also selected you'll have to select the lasso tool and hold alt and drag selections around any areas you don't want selected

3. Select > modify > expand

4. You need to expand the region around stars to include their glow, choose to grow around 4-8 pixels depending on your starfield

5. Now you need to feather the edge of each selection so it's soft, goto select > feather and use a figure which is half that of the one you expanded with 

6. Now the theory bit, I think you can just press delete and it'll ask you if you want to heal selection (or it may be a menu option). It will use ai synthesis (I'm guessing it's exactly the same as how starnet etc work) to sample surrounding pixels and fill in the empty space with similar values. You should then be left with a starless image.

Point 6 is the theory as I haven't tried it myself, but it's also exactly how a GIMP plugin I use works too, think it's called "Resynthesiser"

As I said, you can just process with the stars in, I havent really found too much difference between stars and starless processing other than your star colours tend to over saturate and they bloat.

Edited November 14, 2022 by Elp

[Elp]

You can also use the above to do star minimisation if your field has lots of stars in it to put more focus on the target. Instead of step 6 you do:

Filter > other > minimum

And use a value of 1 usually.

You can also apply a light Gaussian blur whilst your stars are selected to remove any diffraction anomalies (not Newtonian diffraction spikes).

Edited November 14, 2022 by Elp